Chula Vista police said the boys had gotten into some trouble at school, left Rancho del Rey Middle School around 11 a.m. and did not go home that night.

Saunders was reunited with his family early Tuesday after spending the long weekend on the run with his friend and spending his 13th birthday away from home. Saunders said he and Navarro slept in an RV and outside for a few days before he decided to head back home.

Runaway Tween Describes Trip to Mexico

A tween who ran away to Mexico with his friend explains why and how they crossed the border on their own. NBC 7's Megan Tevrizian reports.

(Published Tuesday, Sept. 10, 2013)

Saunders and his friend Jermayn Navarro planned to run away after school on Friday, Saunders told NBC 7 News in an exclusive interview. His family said grades and other challenges were starting to come to a breaking point and Sammy wasn't prepared to face the consequences.

Seated between his parents on his family room couch, Saunders told how the boys walked more than 11 miles to the San Ysidro Port of Entry and then, along with two adults, made it through the pedestrian crossing into Tijuana.

“We stood next to an adult and walked through,” he explained.

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NBC 7's Chris Chan reports on two 12-year-old runaways who have been missing for three days after walking from Rancho del Rey Middle School.

(Published Tuesday, Sept. 10, 2013)

“My plan was like to follow him,” Sammy said of his friend. “But once I got to Mexico, I knew that was the wrong decision.”

They ended up sleeping in an RV lent to them by a friend of Navarro’s, the boy said.

Sammy, who had never been to Mexico, said he was fascinated by the experience at first.

But he didn't speak the language and after seeing what he described as scary things, he decided it was time to return home.

On Monday, he saw a Mexican police patrol car and turned himself in. The officer then contacted the U.S. Border Patrol and Chula Vista police.

After a series of phone calls, the Saunders family was reunited in the early morning hours Tuesday.

“Just happy to see him,” said father, Terry Saunders. “Happy that he was in one piece.”

Terry and Clara Saunders did everything they could to get the word out about their missing son. They used Facebook to alert friends and family, posted flyers, called friends and law enforcement agencies.

When they learned their son had been found by the authorities in Mexico, they were thrilled.

Sammy had this advice to other children considering the same kind of adventure, “Stay home and deal with it.”

As for Navarro, authorities say he ran away when he spotted police officers in Mexico Monday night. On Tuesday morning, detectives said they believed Navarro was with extended family in Mexico.

By 4:05 p.m., officials confirmed Navarro was safe, and had been reunited with his immediate family.

NBC 7 spoke with the boy on Tuesday who said he ran away because a teacher took his laptop away and allegedly called him stupid.

Navarros said he crossed the border and befriended homeless people, who gave him money for food.

On the streets of Mexico, Navarro said he saw gangs and was very scared.

NBC 7 spoke with Navarro's grandmother on Tuesday, who said the boy has never done anything like this before. The grandmother said that days before Navarro ran away, his mother took away his iPod because he was misbehaving in school.